The prior art reveals examples of the concern for an oil filtering system which responds to the situation of a contaminated filter. When the system and the filter are contaminated, the efficiency of the flow of oil, and even the operation of the system itself, are impeded, and it is therefore important that the oil filter be clean and that it be fully functional for its usual purpose of filtering the oil while allowing maximum flow of oil. Examples of prior art concern for a contaminated or clogged oil filter are found in U.S. Pat. Nos. 2,879,892 and 3,482,696 and 3,757,951. The latter patent shows a filter which automatically opens to allow a bypass flow of oil, in the event the filter element becomes clogged. The first two aforesaid patents show oil filter elements with electrical signals, such as warning lamps, which automatically operate in response to a clogged filter condition.
The present invention is also concerned with a signalling system for a clogged filter condition, and it is further concerned with an automatic switching arrangement whereby the oil can be directed from a valve to either or both of two oil filters incorporated in the system. That is, in one mode for the present system, oil can be directed to only one of the filters, and, when that one filter becomes contaminated or clogged, then the system will automatically operate to switch to direct the flow to the other clean filter. Simultaneous with the aforementioned, a signal, such as a warning light or buzzer or the like, can be activated to notify the operator that the first filter is clogged and therefore needs changing. Additionally, the present system is arranged such that oil can be directed to both of the filters at one time, if and when that arrangement is desirable, and that time could be when the oil is cold and is therefore of a higher viscosity and would normally be impeded in its flow through a single filter element. Accordingly, the present invention incorporates a temperature switch which senses the temperature of the oil in the system and which therefore affects the setting of the valve which is directing the oil to the filters such that when the oil is cold, it can be directed to both of these filters, for the reason mentioned, and also when the cold oil is directed to both of the filters, there will be no false signal comparable to indicating that a filter is clogged, since the cold oil could act upon the system in the same manner that contaminated oil could act.
Accordingly, the primary objectives of this invention are to accomplish the aforementioned features, and the present invention therefore provides a dual oil filter automatic switching system which operates to switch the oil flow from a contaminated filter to a clean filter.
In summary, precision machinery utilizing hydraulic power requires filtration of the hydraulic fluid. If the filter is not changed when it is dirty, it will clog up and the oil will then bypass the filter and carry its dirt to the delicate machinery, or, if there is no bypass arrangement, the oil lines could break. Accordingly, it is common practice to have filter indicators or switches which operate warning devices to alert the operator of the clogging condition. However, if he does not notice the clogging condition, or if it is not convenient to change the filter, the filter continues to clog until the undesirable consequences occur. The present invention automatically switches the flow of oil from a clogged filter to a clean filter, and it energizes a signal which indicates the clogged condition and thereby informs the operator to replace the dirty filter. Still further, the present invention provides the dual filter arrangement mentioned and wherein even the second filter is provided with a signal which will indicate to the operator when the second filter is clogged. Still further, the present invention provides a temperature sensitive device which takes into account the higher viscosity of cold fluid or oil, and the cold fluid or oil can be sensed so that the system will not falsely switch, or it can be sensed so that the system will set itself into a mode which simultaneously directs the fluid or oil to both of the filters.
Other objects and advantages will become apparent upon reading the following description in light of the accompanying drawings.